Re: 2nd order ODE from 49G+ User Guide -- I get an Error message

On Tuesday, May 15, 2012 2:12:53 PM UTC-5, dg69 wrote:
Hi !

Thank's for your answer... I have made one hundred tests... but without succes.

Just behind these post I've open a new discussion...


"Error on HP50G ODE numeric solver ?!!!"

here is a copy :

--------------

Today with my HP50G ROM 2.15 I try the basic example in chapter 16 from the user guide book...

y'' + 1.962*y' + 18.75*y =0
y'(x=0)=6 and y(x=0)=0

| 0 1 |
|-18.75 -1.962| matrix is store in A

I place 'A*Y' in the "f" field
Indep:X Init:0 Final:2
Soln:Y Init:[0 6]
and the solve command give me:"Non algebraic in expression"


I can't place A*Y (without quotes) in f field as the user guide show... error "Invalid syntax"

I try this way :

'D(Y)' in the f field

D contain the program <<->Y << A Y * >> >> But the same error occur...

When i come back to the VAR menu the var Y=[0 6] X=0 and EQ are there with good initial values...

I try these:

If I place on the edit line 'A*Y' then ENTER the stack show A*Y if I try EVAL the i have the same error "Non algebraic expression" is there something wrong ?

If I place on the stack the vector [0 6] the press D program the result is OK... [6 -11.772] but 'D(Y)' ENTER EVAL give the "Non algebraic expression" error.


Before sending these message I search in old contribution and i found in 2003 year a same problem but with a HP49G... Jean-Yves Avenard wrote "This was a bug fixed in ROM 1.20 of the 49G+ .. "

I did something wrong ?

Thank's for your help.

Didier.


----

In HPcalc.org I can see three versions (1+two updates) of these ROM2.15... Is there a way to identify the 2.15 in my HP50G ?

Let's address things one at a time.

- for etiquette, you should only run one forum thread for a problem.

- the identical exercise is in the 50G users guide page 16-61. You may get additional help if forum members are aware of that reference.

- The reason you cannot enter the equation A*Y in the f: entry field without single quotations around it is because you are in RPN mode. The exercise screen shots in both the 49 & 50 manuals were taken from a calculator operating in algebraic mode.

- to give you a clean start at solving this equation, would suggest the following:
{A Y X PPAR} ENTER
PURGE

- the variable EQ should have no bearing on the exercise. This must be a left over variable from some other activity that you have performed.

- MAKE SURE you have no global variables with the same name that you are trying to use for this example. Are you starting the numeric solver-solve diff eq while in the HOME directory or some other directory?

- until you get past your initial problems, I would suggest NOT trying to introduce defined functions (your D(Y) equation). Get the basic example to work first. Then you can try the defined function.

- now go back and try entering the equation/initial conditions again.


.